Waste tire thermal cracking system and thermal cracking process

Abstract

The invention discloses a waste tire thermal cracking system which comprises a feeding device, a fluidized bed cracking furnace, a separator, a cooling device, a boiler device and a heat exchange system which are sequentially communicated, and pyrolysis gas output by the cooling device is divided into first pyrolysis gas and second pyrolysis gas. The first pyrolysis gas is input into a heat exchange system, the second pyrolysis gas is input into a boiler device, the system is adopted for carrying out a thermal cracking process, charcoal is separated from first mixed gas output from the fluidized bed cracking furnace through cyclone, and the second mixed gas is output from the fluidized bed cracking furnace. Condensing the obtained second mixed gas in a cooling device to obtain an oil-water mixture so as to extract pyrolytic oil and pyrolysis gas, and dividing the pyrolysis gas into two parts, one part serves as fuel to be input into the boiler to be combusted to form hot flue gas, the other part exchanges heat with the hot flue gas to be heated and flows back into the fluidized bed cracking furnace to serve as hot carrier gas to provide heat and form an inert atmosphere, and energy, resources and pyrolysis gas can be fully utilized by adopting the thermal cracking process of the system.

Description

Technical Field

[0001] The invention relates to the technical field of waste tire resource utilization, in particular to a waste tire thermal cracking system and a thermal cracking process. Background Art

[0002] Waste tires are a type of waste generated as the number of vehicles increases. Their treatment and recycling are crucial to environmental protection and resource recycling. According to the latest statistics, the amount of waste tires generated in China increases at a rate of 8% to 10% each year, but the recycling rate is only about 50%, which leads to environmental pollution and waste of resources.

[0003] Pyrolysis of waste tires is an important waste tire processing and recycling technology, which can treat waste tires at high temperature under anaerobic or anoxic conditions, and crack them to form pyrolysis oil, carbon black, pyrolysis gas and steel wire. German patent DE10219440A1 discloses a low-temperature pyrolysis method and device for rubber products, which is provided with a crusher 3, a reaction vessel 7, a preheater 8, a cracking furnace 9, a pyrolysis gas water cooling device 21, and a cooling device 10. The crusher 3 crushes the waste tires, and the waste tire particles undergo pyrolysis reaction in the reaction vessel 7 and the cracking furnace 9. The pyrolysis gas water cooling device 21 condenses the pyrolysis oil in the gas generated by pyrolysis. The exhaust gas 34 output by the cracking furnace 9, the pyrolysis gas 32 output by the pyrolysis gas water cooling device 21, and the heat output by the cooling device 10 are mixed and recycled to the reaction vessel 7 and the cracking furnace 9, and are used to preheat the reaction vessel 7 and the cracking furnace 9. However, this device and method still wastes a lot of heat and resources, and the pyrolysis gas cannot be fully utilized. Summary of the invention

[0004] In view of the shortcomings of the above-mentioned existing waste tire thermal cracking system that cannot fully utilize the heat and pyrolysis gas generated during the thermal cracking reaction and causes waste of resources, the applicant provides a waste tire thermal cracking system with a reasonable structure. The system first condenses the first mixed gas with an oil-gas mixture generated by a fluidized bed cracking furnace to extract pyrolysis oil, and then divides the colder pyrolysis gas into two parts, one of which is input into a boiler as fuel to be burned to form hot flue gas, and the other part is heat-exchanged with the hot flue gas to increase its temperature and refluxed into the fluidized bed cracking furnace as a hot carrier gas to provide heat and form an inert atmosphere. The process of thermal cracking using this system can fully utilize energy, resources and pyrolysis gas.

[0005] The technical solutions adopted by the present invention and the technical effects achieved are as follows: A waste tire thermal cracking system comprises a feeding device, a fluidized bed cracking furnace, a separator, a cooling device, a boiler device and a heat exchange system which are connected in sequence, wherein the air outlet of the cooling device is connected with the air inlet of the boiler device and the refrigerant inlet of the heat exchange system respectively, the pyrolysis gas output by the cooling device is divided into a first pyrolysis gas and a second pyrolysis gas, the first pyrolysis gas is input into the heat exchange system, and the second pyrolysis gas is input into the boiler device, the heat medium outlet of the heat exchange system is connected with the air inlet of the fluidized bed cracking furnace, and the heat exchange system outputs the third pyrolysis gas after heat exchange and refluxes to the fluidized bed cracking furnace.

[0006] The first mixed gas output from the fluidized bed cracking furnace is separated into biochar through a cyclone, and the obtained second mixed gas can be condensed in a cooling device to obtain an oil-water mixture to extract pyrolysis oil and pyrolysis gas. The pyrolysis gas is then divided into two parts, one part is input into the boiler as fuel to burn to form hot flue gas, and the other part is heat-exchanged with the hot flue gas to increase its temperature and reflux into the fluidized bed cracking furnace as a hot carrier gas to provide heat and form an inert atmosphere. The process of thermal cracking using this system can make full use of energy, resources and pyrolysis gas.

[0007] As a further improvement of the above technical solution: The separator is a cyclone separator, and the cooling device is a spray device.

[0008] The cyclone separator is used to separate the gas and small particles of biochar in the first mixed gas. The discharge port at the bottom of the cyclone separator can discharge the small particles of biochar, thereby collecting fine particles of carbon black and powdered carbon black. A pre-spray device is placed before the boiler device to cool the second mixed gas to condense the tar therein and form an oil-water mixture in the cooling device to avoid affecting the operation of the system. At the same time, the oil-water mixture is formed after condensation, and high-quality pyrolysis oil can also be formed after subsequent treatment.

[0009] The system also includes a pre-treatment device, and the waste tire particles crushed by the pre-treatment device are sent to the feeding device.

[0010] The pretreatment device is used to crush the waste tires into particles so as to fully react in the fluidized bed pyrolysis furnace.

[0011] The system also includes a flue gas treatment system, and an air inlet of the flue gas treatment system is connected to a refrigerant outlet of the heat exchange system.

[0012] The hot flue gas is purified by the flue gas treatment system to remove harmful components and is discharged to the outside after meeting the emission standards.

[0013] A process for thermal cracking of waste tires using the thermal cracking system of claim 1, comprising the following steps: S1: waste tire particles are fed into a fluidized bed pyrolysis furnace by a feeding device, and undergo a thermal cracking reaction in the fluidized bed pyrolysis furnace to form large-particle biochar and a first mixed gas. The large-particle biochar is discharged from the discharge port of the fluidized bed pyrolysis furnace, and the first mixed gas is input into a separator; S2: the first mixed gas is separated into small biochar particles and a second mixed gas in a separator, the small biochar particles are discharged from a discharge port of the separator, and the second mixed gas is input into a cooling device; S3: The second mixed gas is cooled by a cooling device, and the second mixed gas is condensed to form pyrolysis gas and an oil-water mixture, and the oil-water mixture is discharged from the cooling device, and the pyrolysis gas is divided into a first pyrolysis gas and a second pyrolysis gas, which are respectively input into a heat exchange system and a boiler device; S4: air is introduced into the boiler device, the second pyrolysis gas is burned in the boiler device, and the generated hot flue gas is input into the heat exchange system from the heat medium inlet, and the first pyrolysis gas is input into the heat exchange system from the cold medium inlet, and the first pyrolysis gas is heat-exchanged with the hot flue gas in the heat exchange system to form a high-temperature third pyrolysis gas; S5: The third pyrolysis gas flows back to the fluidized bed cracking furnace from the heat medium outlet of the heat exchange system.

[0014] As a further improvement of the above technical solution: The ratio of the first pyrolysis gas to the second pyrolysis gas is 1:1.

[0015] The first pyrolysis gas and the second pyrolysis gas are cooled to 30-100°C by a cooling device, the hot flue gas formed by the combustion of the second pyrolysis gas in the boiler device is 850-1000°C, the first pyrolysis gas is heat exchanged with the hot flue gas in a heat exchange system, the hot flue gas is cooled to 300-400°C, the third pyrolysis gas after heat exchange is heated to 650-750°C, and the working temperature in the fluidized bed cracking furnace is 500-600°C.

[0016] The cooling device cools down the second mixed gas, and the tar in the second mixed gas is condensed into an oil-water mixture, which can be directly discharged from the cooling device 5 to avoid blockage, corrosion and the like in subsequent devices, thereby avoiding affecting the operation of the system. The oil-water mixture can also form high-quality pyrolysis oil after subsequent treatment, thereby improving economic benefits. The first pyrolysis gas and the second pyrolysis gas are set to a ratio of 1:1. After the second pyrolysis gas is burned and heated, it exchanges heat with the first pyrolysis gas to form a high-temperature third pyrolysis gas that flows back to the fluidized bed cracking furnace. The third pyrolysis gas does not contain oxygen and is also an inert gas. It flows back to the fluidized bed cracking furnace as a hot carrier gas to provide heat and form an inert atmosphere, thereby achieving full utilization of resources and avoiding insufficient thermal cracking reaction in the fluidized bed cracking furnace.

[0017] When the combustion heat in the boiler device reaches the requirement and the system heat balance can be achieved, the molar ratio of the air introduced into the boiler device to the second pyrolysis gas is 1:1.

[0018] The method also includes the following steps: when the temperature of the third pyrolysis gas after heat exchange is insufficient, natural gas is introduced into the boiler device, and the second pyrolysis gas, air and natural gas are burned together to increase the temperature of the hot flue gas.

[0019] The boiler device is used to increase the temperature of the input second pyrolysis gas. Air is introduced into the boiler device to burn together with the second pyrolysis gas to form a large amount of hot flue gas. If the pyrolysis gas output by the cooling device is not burned by the boiler device but directly returned to the fluidized bed cracking furnace, the reaction heat in the fluidized bed cracking furnace is insufficient, and the system energy and energy balance cannot be achieved. Compared with the additional use of oil as fuel, using the second pyrolysis gas as fuel can avoid clogging the feed port of the boiler device and coking in the boiler device, and fully utilize the second pyrolysis gas to achieve energy conservation and emission reduction, reduce costs, and reduce energy loss. If the heat of the refluxed third pyrolysis gas is not enough, it will affect the heat balance of the system. Therefore, natural gas can be introduced into the boiler device, and natural gas, air, and the second pyrolysis gas can be burned together to increase the temperature of the hot flue gas, thereby increasing the temperature of the third pyrolysis gas after heat exchange.

[0020] The method also includes the following steps: the hot flue gas after heat exchange by the heat exchange system is purified by the flue gas treatment system and discharged to the outside after meeting the emission standards. The flue gas treatment system is used to purify the flue gas output by the heat exchange system until it meets the emission standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of the system of the present invention.

[0022] Figure 2 It is a process flow chart of the present invention.

[0023] In the figure: 1. Pretreatment device; 2. Feeding device; 3. Fluidized bed cracking furnace; 4. Separator; 5. Cooling device; 6. Boiler device; 7. Heat exchange system; 8. Flue gas treatment system. DETAILED DESCRIPTION

[0024] The specific implementation of the present invention is described below in conjunction with the accompanying drawings.

[0025] like Figure 1 , 2As shown, the waste tire thermal cracking system of the present invention comprises a pretreatment device 1, a feeding device 2, a fluidized bed cracking furnace 3, a separator 4, a cooling device 5, a boiler device 6, a heat exchange system 7, and a flue gas treatment system 8 which are sequentially connected. The air outlet of the cooling device 5 is respectively connected to the air inlet of the boiler device 6 and the refrigerant inlet of the heat exchange system 7, and the heat medium outlet of the heat exchange system 7 is connected to the air inlet of the fluidized bed cracking furnace 3.

[0026] The crusher of the pretreatment device 1 is used to crush waste tires, which can be car tires, motorcycle tires, truck tires or other types of tires. After crushing, the particle size can be ≤3mm, which is convenient for subsequent full reaction.

[0027] A thermal cracking reaction occurs in the fluidized bed cracking furnace 3, which can convert waste tire particles into combustible gas and large-particle biochar. The fluidized bed cracking furnace 3 has a bottom air inlet, a discharge port, and a top air outlet. The discharge port discharges large-particle biochar, and the air outlet outputs the gas generated during the thermal cracking process to the separator 4. The air inlet is used to input the third pyrolysis gas refluxed by the subsequent heat exchange system 7. On the one hand, this part of the pyrolysis gas can provide heat for the fluidized bed cracking furnace 3 and create an inert atmosphere. On the other hand, because the components of the pyrolysis gas are similar to those of the gas generated by the cracking reaction, it will not affect the cracking reaction. In addition, using the pyrolysis gas as the heat carrier gas phase will not bring in oxygen, so that the waste tires can be fully cracked.

[0028] The separator 4 is connected to the gas outlet of the fluidized bed pyrolysis furnace 3. The separator 4 is used to separate the first mixed gas input from the fluidized bed pyrolysis furnace 3. The separation can obtain a second mixed gas and small-particle biochar. The discharge port at the bottom of the separator 4 can discharge the small-particle biochar, thereby collecting fine-particle carbon black and powdered carbon black. In this embodiment, the separator 4 is a cyclone separator.

[0029] The cooling device 5 can cool down the second mixed gas input by the separator 4. Since the second mixed gas contains a large amount of tar, it will condense when the temperature is <400°C. If it is not treated and directly enters the subsequent device, it will cause blockage, corrosion and other phenomena, affecting the operation of the entire system. Therefore, a cooling device 5 is placed before the boiler device 6. In this embodiment, the cooling device 5 is a spray device, which sprays water to cool the second mixed gas. The tar in the second mixed gas is condensed into an oil-water mixture, which can be directly discharged from the cooling device 5 to avoid affecting the operation of the system. The oil-water mixture can also be formed into high-quality pyrolysis oil after subsequent treatment, thereby improving economic benefits. The pyrolysis gas in the second mixed gas is divided into a first pyrolysis gas and a second pyrolysis gas, which are respectively input into the heat exchange system 7 and the boiler device 6, and the ratio of the first pyrolysis gas to the second pyrolysis gas is 1:1.

[0030] The boiler device 6 is used to increase the temperature of the input second pyrolysis gas. Air is introduced into the boiler device 6 to burn together with the second pyrolysis gas to form a large amount of hot flue gas. If the pyrolysis gas output by the cooling device 5 is not burned by the boiler device 6 but directly returned to the fluidized bed cracking furnace 3, the reaction heat in the fluidized bed cracking furnace 3 is insufficient, and the system energy and energy balance cannot be achieved. Compared with the additional use of oil as fuel, using the second pyrolysis gas as fuel can avoid clogging the feed port of the boiler device 6 and avoiding coking in the boiler device 6, and fully utilizing the second pyrolysis gas to achieve energy conservation and emission reduction, reduce costs, and reduce energy loss.

[0031] In the heat exchange system 7, the hot flue gas discharged from the boiler device 6 exchanges heat with the first pyrolysis gas output by the cooling device 5, and after the heat exchange, a third pyrolysis gas with a higher temperature is formed and refluxes to the fluidized bed cracking furnace 3 to act as a hot carrier gas to provide heat and form an inert atmosphere, thereby providing heat for the thermal cracking reaction.

[0032] The flue gas treatment system 8 is used to purify the hot flue gas output by the heat exchange system 7 until it meets the emission standards.

[0033] When the system is actually working, waste tires with a moisture content of ≤20% are input into the pretreatment device 1, and the pretreatment device 1 crushes the waste tires. The waste tire particles are fed into the fluidized bed pyrolysis furnace 3 by the feeding device 2, and contact and fully react with the high-temperature hot carrier gas input from the bottom of the fluidized bed pyrolysis furnace 3. The hot carrier gas here is the third pyrolysis gas output by the subsequent heat exchange system 7. The residence time of the waste tire in the furnace of the fluidized bed pyrolysis furnace 3 is 30min-60min, the furnace operating temperature is 500-600℃, and the operating pressure is 8-15kPa, which can ensure that the waste tire particles undergo sufficient pyrolysis reaction in the fluidized bed pyrolysis furnace 3 to form a first mixed gas with large-particle biochar and a large amount of material. The large particles of biochar are discharged from the lower part of the fluidized bed pyrolysis furnace 3 and then collected. The first mixed gas passes through the top of the fluidized bed pyrolysis furnace 3 and enters the separator 4 for solid-gas separation. The small particles of biochar in the gas are separated by the separator 4 and then discharged from the lower part. The gas portion after solid-gas separation is the second mixed gas. The second mixed gas contains pyrolysis gas and tar, which is input into the cooling device 5 from the separator 4 and cooled by spraying water. The tar in the second mixed gas is condensed to form an oil-water mixture and is discharged from the cooling device 5. After subsequent treatment, high-quality pyrolysis oil can be formed. The pyrolysis gas in the second mixed gas is cooled to 30-100°C by spraying. The pyrolysis gas is divided into the first pyrolysis gas and the second pyrolysis gas, which are respectively input into the heat exchange system 7 and the boiler device 6. The second pyrolysis gas input into the boiler device 6 is used as fuel and burns together with the air to form a large amount of hot flue gas with a temperature of 850-1000°C. The ratio of air to the second pyrolysis gas is a molar ratio of 1:1. The hot flue gas is then input into the heat exchange system 7 to exchange heat with the relatively cold first pyrolysis gas. The hot flue gas is cooled to 300-400°C, and the first pyrolysis gas is heated to form a third pyrolysis gas with a temperature of 650-750°C. The third pyrolysis gas flows back to the fluidized bed cracking furnace 3 as a hot carrier gas to provide heat and form an inert atmosphere. If the heat of the refluxed third pyrolysis gas is not enough, it will affect the heat balance of the system. Therefore, natural gas can be introduced into the boiler device 6, and natural gas, air, and the second pyrolysis gas are burned together to increase the temperature of the hot flue gas, thereby increasing the temperature of the third pyrolysis gas after heat exchange. The hot flue gas is purified by the flue gas treatment system 8 to remove harmful components and is discharged to the outside after meeting the emission standards.

[0034] The above description is an explanation of the present invention, not a limitation of the present invention. The present invention may be modified in any form without violating the spirit of the present invention.

Claims

1. A waste tire thermal cracking system, characterized by: The invention comprises a feed device (2), a fluidized bed cracking furnace (3), a separator (4), a cooling device (5), a boiler device (6) and a heat exchange system (7) which are connected in sequence. The air outlet of the cooling device (5) is connected to the air inlet of the boiler device (6) and the refrigerant inlet of the heat exchange system (7) respectively. The pyrolysis gas output by the cooling device (5) is divided into a first pyrolysis gas and a second pyrolysis gas. The first pyrolysis gas is input into the heat exchange system (7) and the second pyrolysis gas is input into the boiler device (6). The heat medium outlet of the heat exchange system (7) is connected to the air inlet of the fluidized bed cracking furnace (3). The heat exchange system (7) outputs the third pyrolysis gas after heat exchange and refluxes it to the fluidized bed cracking furnace (3).

2. The waste tire thermal cracking system according to claim 1, characterized in that: The separator (4) is a cyclone separator, and the cooling device (5) is a spray device.

3. The waste tire thermal cracking system according to claim 1, characterized in that: The system further comprises a pre-treatment device (1), and the waste tire particles crushed by the pre-treatment device (1) are fed into the feeding device (2).

4. The waste tire thermal cracking system according to claim 1, characterized in that: The system further comprises a flue gas treatment system (8), wherein an air inlet of the flue gas treatment system (8) is connected to a refrigerant outlet of the heat exchange system (7).

5. A process for thermal cracking of waste tires using the thermal cracking system of claim 1, characterized in that: The following steps are involved: S1: waste tire particles are fed into a fluidized bed pyrolysis furnace (3) by a feeding device (2), and undergo a thermal cracking reaction in the fluidized bed pyrolysis furnace (3) to form large-particle biochar and a first mixed gas. The large-particle biochar is discharged from a discharge port of the fluidized bed pyrolysis furnace (3), and the first mixed gas is input into a separator (4); S2: the first mixed gas is separated into small-particle biochar and a second mixed gas in a separator (4), the small-particle biochar is discharged from a discharge port of the separator (4), and the second mixed gas is input into a cooling device (5); S3: the second mixed gas is cooled by a cooling device (5), and the second mixed gas is condensed to form pyrolysis gas and an oil-water mixture, the oil-water mixture is discharged from the cooling device (5), and the pyrolysis gas is divided into a first pyrolysis gas and a second pyrolysis gas, which are respectively input into a heat exchange system (7) and a boiler device (6); S4: air is introduced into the boiler device (6), the second pyrolysis gas is burned in the boiler device (6), and the generated hot flue gas is input into the heat exchange system (7) from the heat medium inlet, the first pyrolysis gas is input into the heat exchange system (7) from the cold medium inlet, and the first pyrolysis gas is heat-exchanged with the hot flue gas in the heat exchange system (7) to form a high-temperature third pyrolysis gas; S5: The third pyrolysis gas flows back into the fluidized bed cracking furnace (3) from the heat medium outlet of the heat exchange system (7).

6. The thermal cracking process according to claim 5, characterized in that: The ratio of the first pyrolysis gas to the second pyrolysis gas is 1:

1.

7. The thermal cracking process according to claim 5, characterized in that: The first pyrolysis gas and the second pyrolysis gas are cooled to 30-100° C. by the cooling device (5); the second pyrolysis gas is burned in the boiler device (6) to form hot flue gas of 850-1000° C.; the first pyrolysis gas is heated in the heat exchange system (7) by heat exchange with the hot flue gas, and the hot flue gas is cooled to 300-400° C.; the third pyrolysis gas is heated to 650-750° C. after the heat exchange; and the working temperature in the fluidized bed cracking furnace (3) is 500-600° C.

8. The thermal cracking process according to claim 5, characterized in that: When the combustion heat in the boiler device (6) reaches the requirement and the system heat balance can be achieved, the molar ratio of the air introduced into the boiler device (6) to the second pyrolysis gas is 1:

1.

9. The thermal cracking process according to claim 5, characterized in that: The following steps are also included: When the temperature of the third pyrolysis gas after heat exchange is insufficient, natural gas is introduced into the boiler device (6), and the second pyrolysis gas, air, and natural gas are burned together to increase the temperature of the hot flue gas.

10. The thermal cracking process according to claim 5, characterized in that: The following steps are also included: The hot flue gas after heat exchange in the heat exchange system (7) is purified by the flue gas treatment system (8) and discharged to the outside after meeting the emission standards.

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